What is the title of shakugan no shana song?

The song you're referring to is most likely "Hishoku no Sora (Crimson-Colored Sky)". It is the opening theme song for the anime series Shakugan no Shana, which is also known as Shakugan no Shana: Burning-Eyed Shana. The song is performed by Yoko Takahashi, a renowned Japanese singer who is known for her contributions to the anime and video game music scene.